lazy_instance_variable.rb

# =============================
# Spell: Lazy Instance Variable
# =============================

# Wait until the first access to initialize an instance variable.

class C
  def attribute
    @attribute = @attribute || "some value"
  end
end

obj = C.new
obj.attribute # => "some value"

# For more information: http://www.pragprog.com/titles/ppmetr/metaprogramming-ruby